The teacher presents the animation resource called «Inclined plane: A simple machine» in which the notion of slope is contextualized from different situations. The introduction will generate discussion around the definition of slope and its characteristics. The objective is to analyze the properties of positive and negative correlation between variables, of either linear variation or direct and inverse proportion in arithmetic and geometric contexts. To identify relations between properties of the graphs and its algebraic representation. To recognize the relation between the algebraic representation of a straight line and its graph.